1. Field of the Invention
The present invention relates generally to a method of staining the surface of the eye, and more specifically to a method of staining the surface of the eye with a dry dye introduced directly onto the surface of the eye.
2. Background
Physicians regularly employ staining of the surface of the eye to aid in the diagnosis of various eye conditions. Dyes used for this purpose include Fluorescein, Lissamine Green, and Rose Bengal. Staining can aid in the diagnosis of corneal abrasion, infection, injury or trauma to the eye, foreign bodies in the eye, abnormal tear production, and dry eye, including severe dry eye such as keratoconjunctivitis sicca. Proper diagnosis of an eye condition aids the physician in selecting the appropriate treatment.
Dry eye disease is one of the most common conditions encountered by primary eye care physicians. Fluorescein staining is considered one of the most valuable tests in diagnosing dry eye disease. Typically, a length of filter paper or other substrate impregnated with Fluorescein dye is touched to the surface of the eye, allowing the dye to be introduced onto the cornea. Blinking by the patient spreads the dye, which readily diffuses into the tear film of the eye. The dye is then generally visualized under a cobalt blue lamp. The integrity of the tear film can be assessed by measuring the tear-film break up time while the eye is under the cobalt blue light. Further, corneal staining by the dye can indicate corneal injury, secondary to dry eye or due to other causes, as well as localized depressions in the eye resulting from prolonged dryness. The level of staining visualized under the cobalt blue lamp is indicative of the severity of the condition.
Lissamine Green and Rose Bengal are also used to diagnose eye conditions, including dry eye. These dyes are useful in detecting dead or devitalized cells on the corneal surface, as well as on the conjunctiva. Introduction of these dyes into the eye of a patient is performed in the same manner as the introduction of Fluorescein.
While the dyes described above, as well as others, are valuable in diagnosing disorders of the eye, the method of introduction of the dye into the eye can be problematic. Because the filter paper or other substrate used is contacted directly with the surface of the eye, there is a risk of introduction of bacteria onto the eye surface. Further, the substrate is often made wet with saline solution prior to introduction onto the eye, increasing the chance of introducing microorganisms onto the eye if the saline solution is not properly sterile. Use of a substrate such as filter paper can also abrade the cornea or conjunctiva of the eye. These risks are associated with the introduction of any physical object onto the surface of the eye. In some cases, liquid drops containing dye may be used to avoid contact with the eye. Such liquids, however, are susceptible to bacterial growth and as such still carry the risk of infection.